A number of different methods and systems are known in the art for creating depth maps. In the present patent application and in the claims, the term “depth map” refers to a representation of a scene as a two-dimensional matrix of pixels, in which each pixel corresponds to a respective location in the scene and has a respective pixel depth value, indicative of the distance from a certain reference location to the respective scene location. In other words, the depth map has the form of an image in which the pixel values indicate topographical information, rather than brightness and/or color of the objects in the scene. The terms “depth map” and “3D map” are used herein interchangeably and have the same meaning.
Depth maps may be created, for example, by detection and processing of an image of an object onto which a pattern of spots is projected. In some such systems, the positions of the spots are uncorrelated in planes transverse to the projection beam axis. The positions are “uncorrelated” in the sense that the auto-correlation of the positions of the speckles in the pattern as a function of transverse shift is insignificant for any shift larger than the spot size. Random patterns, such as those created by primary laser speckle, are uncorrelated in this sense. Patterns created by human or computer design, such as pseudo-random and quasi-random patterns, may also be uncorrelated. Depth mapping methods using these sorts of projected patterns are described, for example, in PCT International Publications WO 2007/043036, WO 2007/105205, WO 2008/120217, and WO 2010/004542, whose disclosures are incorporated herein by reference.
Depth maps may be processed in order to segment and identify objects in the scene. Identification of humanoid forms (meaning 3D shapes whose structure resembles that of a human being) in a depth map, and changes in these forms from scene to scene, may be used as a means for controlling computer applications. For example, PCT International Publication WO 2007/132451, whose disclosure is incorporated herein by reference, describes a computer-implemented method in which a depth map is segmented so as to find a contour of a humanoid body. The contour is processed in order to identify a torso and one or more limbs of the body. An input is generated to control an application program running on a computer by analyzing a disposition of at least one of the identified limbs in the depth map.
As another example, U.S. Patent Application Publication 2011/0052006, whose disclosure is incorporated herein by reference, describes a method for processing a temporal sequence of depth maps of a scene containing a humanoid form. A digital processor processes at least one of the depth maps so as to find a location of the head of the humanoid form, and estimates dimensions of the humanoid form based on this location. The processor tracks movements of the humanoid form over the sequence using the estimated dimensions.